It's a useful text for intermediate level students who need a vocabulary boost and grammar review. Each unit is clear and easy to understand. Third-year middle school Korean students have learned a lot from it.
There is one mistake though, on a page 101 matching exercise: "After the workshop, I was as tired... " "...as if I hadn't slept for a week."
the 'as... as if' combination is frankengrammar, an invalid combination of forms.
It should have been: I was so tired (remove the first 'as')
Or: I was as tired as someone who hadn't slept for a week (replace the 'as if' with 'as').